You may have heard of composting toilets and are wondering how they work. A whole host of questions are raised for most people when they hear about these products.

A feature image for a blog post about how composting toilets work.

In this post, we’ll supply basic answers to many of the questions that are raised, including how they work. Plus, you’ll learn about the pros and cons, and we offer links to Canadian sources.

What Is a Composting Toilet?

Composting toilets are just that – toilets that convert human waste into compost. In traditional septic systems, waste is broken down by anaerobic (non-oxygen-using) bacteria. In composting toilets, waste is broken down by aerobic (oxygen using) bacteria in a much faster process.

Similar to Garden Compost

Just as a garden compost pile turns yard waste and kitchen scraps into fertilizer with the help of fungi and bacteria, a composting toilet breaks down human waste and toilet paper to produce nutrient-rich compost.

As in a garden compost pile, decomposition reduces the volume of waste by 70 to 90 percent.

Around for a Long Time

Composting toilets have been available for more than 40 years and can be found in public and private buildings worldwide.

However, they are not common, and this is likely due to worries about odor and disease. Properly constructed and maintained composting toilets destroy infectious agents to produce a safe end-product with a dirt-like consistency and little or no odor.

Removable Time Varies

How often the compost is removed will depend on the type of design or system you’re using. And generally, it is only recommended to be used with ornamental plants, not with those for consumption.

How Does a Composting Toilet Work?

Designs vary. Some large designs require a significant amount of space (usually in a basement) to contain waste and compost, while small models can be placed within a bathroom.

Basic Common Components

Parts of a composting toilet generally include a chamber to hold waste and compost and an air intake and exhaust system to supply the chamber with oxygen and to remove byproducts of decomposition.

Draining and Heat

Usually, a method of draining excess liquid is also included, and in cold climates, it may be necessary to provide heat for the chamber in winter to ensure that composting continues to take place.

Just as in garden compost piles, the right amount of heat, aeration, and moisture are key ingredients for optimal composting. 

Designs with Several Chambers

Some designs (batch composters) use several chambers; when one chamber is filled, it is left to produce compost while the other collects waste.

Other designs (continuous composters) use a single chamber; compost is collected from the bottom while waste is added to the top.

Passive Designs

Some designs are completely passive, allowing bacteria and fungi to do their work without help, while others are active, using mixers and heaters to ensure optimal conditions and speed decomposition.

Active Means Less Space

Active composting toilets require less space since waste is converted to compost more quickly. A variety of composting toilets are on the market, and there are also many plans available for do-it-yourselfers.

NOTE: If you decide to install a composting toilet in your home, you’ll need to check out the local regulations to determine what’s allowed in your location. What’s permissible can vary from region to region.

Advantages of Composting Toilets

There are environmental and practical advantages to using composting toilets. Since no water is used, they significantly reduce water consumption (in developed countries, traditional toilets account for the highest percentage of daily water use).

Save Large Amounts of Water

Using composting toilets instead of traditional models could save up to 40,000 gallons of water per year.

Composting toilets are excellent for areas without sewage hookups. Unlike traditional pit toilets and outhouses, composting toilets keep waste out of the environment until it is no longer harmful.

Good for Developing Countries

In developing countries or rural areas in developed countries, composting toilets are a great way to deal with waste without fear of environmental or sanitation problems.

Depending on local regulations, the compost produced can then be used to fertilize landscaping, returning nutrients to the environment instead of wasting them.

For those without a garden compost pile, kitchen waste can also be added to composting toilets to augment the final product. You’ll need to check the instructions for your unit to see if this is a good idea.

Disadvantages of Composting Toilets

Composting toilets require more maintenance than traditional toilets. If not maintained properly, odors and a buildup of pathogens can result; if improperly composted waste is used to fertilize plants, health problems could result.

Be Prepared for Maintenance

Because of this possibility, even though the compost produced is perfectly safe if the composting toilet is operated and maintained properly, local regulations may forbid the use of it, in which case the compost would need to be removed and placed in a landfill.

Composting toilets usually require other components. Most models need a power source to run the air intake and exhaust systems, and a greywater system and/or septic tank or trench is necessary for most composting toilets since excess liquid must be drained.

Common Questions about Composting Toilets

Here are some common questions about composting toilets:

Question: Do composting toilets really work?
Answer: Yes, they do, if they’re set up and maintained properly.

Question: Can you pee in a composting toilet?
Answer: Yes, you can.

Question: Do you have to empty a composting toilet?
Answer: Yes, you do. How often it’s required will depend on the design of the unit and how much use it gets.

Question: What do you do with the waste from a compost toilet?
Answer: It can be used as fertilizer for ornamental plants, but not those for consumption. Or it can go to the landfill. It’s a good idea to check your local regulations.

Despite the potential drawbacks, household composting toilets are relatively simple to install and maintain. Especially in areas where water is scarce, they can be an important component in eco-friendly home design.

6 thoughts on “How Composting Toilets Work”

  1. Hi Stella, 

    This is a great product for the right location. Coming from a construction and maintenance background I`ve had my fair share of toilet blockages and maintenance checks. I think the compost toilets would be great in remote areas and farming or agricultural applications as emptying and using the compost would be effective. In a world where we are now looking at recycling and environmental products, these toilets definitely have a place. They are also used more in developing countries due to the remote areas and no main sewage system. 

    Great article, thank you


    1. Yes, you’re right. There are many situations where a composting toilet makes a lot of sense, and hopefully, they’ll play an increasingly greater role in waste management everywhere.

  2. This is a very educational post on composting toilets and how they work. We currently have a septic tank on our property, and I have been wondering what the difference is between a septic tank and a composting toilet. 

    I think a composting toilet would be perfect for anybody that lives in a remote area and the water saving feature makes it great for areas where water is scarce. A composting toilet is a brilliant option for anybody that wants to live off-grid as well. 

    1. Yes, they haven’t been as popular in North America as in other parts of the world, but there are loads of practical applications for a composting toilet.

  3. This is a really good article on composting toilets. It makes me want one. The idea of saving 40,000 gallons of water a year is very attractive! But I do know that I have not been successful in getting a kitchen compost heap to work properly. So, I’m not sure how I would do with one of these products.

    1. Yes, they are a tempting way to save water and be more eco-friendly. If you have a lot of doubts and questions, it is probably a good idea to do a lot of research and talk to people who own one or the professionals who work with them before making a final decision.

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